1. Field of the Invention
The present invention generally relates to HVAC (heating, ventilating and air conditioning) systems, and more particularly relates to systems and methods for delivering air to areas of a building by the use of a dual duct system which converts to a multiple zoned single duct system at the delivery end.
2. Background Information
There are a number of ways of heating rooms within a commercial building, but one method currently in use is the use of a double duct system. In a double duct system, one duct delivers cool air from a cool air source such as an air conditioning unit, and another duct delivers warm air from a heater. The two ducts are routed to each room or heating and cooling zone of a building. At the room or heating and cooling zone, the cool air and warm air are mixed according to the temperature needs of that specific room or zone. Thus, each room or zone has two ducts delivered into a mixing chamber, and it also has two dampers which open and close both ducts to deliver the right amount of hot and cold air to achieve the desired temperature of air for delivery to the room or zone. A computer can be utilized and a method called variable air volume (VAV) can be utilized so that each room gets the desired volume and temperature of air it requires, and the temperature of the cold air and the hot air is adjusted to best meet the needs of all of the rooms.
A disadvantage of a conventional dual duct system is that it is expensive to install, because two complete ducting systems must be delivered to each room or zone to be heated or cooled, and two computer controlled VAV dampers are required in each room or zone to be heated and cooled. If similar performance could be achieved while having only one duct routed to each room or zone, then significant savings could be achieved in the cost of ducting, dampers, mixing chambers and the labor involved in installation. Energy savings could be achieved in a system in which the conditioned air is generally not mixed from hot or cold air.
The invention is a double duct changeover HVAC system, which provides a simple, and effective means for economically controlling the temperature and air flow in buildings. The system utilizes two conditioned air sources. In one configuration of the system, one conditioned air source provides warm air, and the other conditioned air source provides cool air. Certain advantages are achieved if one or both of the conditioned air sources also have the ability to produce hot or cold air depending upon the demands of the heating and cooling zones. Air from the first and second conditioned air source is blown by a fan into a first and second main duct system. However, unlike the prior art, these two duct systems, which typically would contain air of different temperatures, are not ducted directly into each room or heating and cooling zone. In this description, it is to be understood that a room is a heating and cooling zone, but several rooms can also make up a single heating and cooling zone. When a xe2x80x9croomxe2x80x9d is referred to, what is meant is a heating and cooling zone.
In one configuration of the invention, a building or floor to be heated is divided into exterior exposures. This would typically be four exterior exposures, representing the four sides of the building, but more than four exterior exposures are also possible if certain areas of the building experienced unique sun or wind exposure. In general, all of the heating and cooling zones or rooms within a particular exterior exposure would be subjected to similar exposure to the sun, shade of the building, wind exposure and other exterior environmental factors. For instance, all of the heating and cooling zones on a north facing side of building would be in one exterior exposure, and they would generally be subjected to similar sun exposure and heat loss. Similarly, all the rooms or heating and cooling zones on the south side of a building could also be in the same exterior exposure. Those rooms would be expected to have similar exposure to sun and heat loss to each other, but could be quite different from the environmental conditions found on the north facing exterior exposure.
In the double duct changeover HVAC system of the invention, air from the first conditioned source and the second conditioned air source is available for each exterior exposure. This can be by ducting branches of the first and second main duct system extending toward each of the four exterior exposures of the typical installation. At some point, near the edge of a particular exterior exposure, the ducts of the first main duct system and the second main duct system would terminate in a Y or T connection and proceed from that point as a single duct. Air through this single duct would be distributed to each of the heating and cooling zones of that particular exterior exposure. Exterior exposure dampers are present in each terminus of the first main duct system and the second main duct system. The exterior exposure dampers variably open or close to regulate the air flowing from each of the first main duct system and the second main duct system, and to control the temperature of air delivered to each room.
However, the individual heating and cooling zones within the exterior exposure would also inevitably have different air flow quantity needs. Achieving the right temperature in any particular heating and cooling zone, when air of a uniform temperature is delivered to each of the exterior exposures, can be accomplished by the system of the invention.
Each of the heating and cooling zones have a sensor for determining the air flow into the room or heating and cooling zone, and the temperature of the room or heating and cooling zone. Based upon the heating and cooling needs of each room, a damper at each room would open or close to deliver the right volume of air to each room to achieve the desired temperature and airflow. The temperature of air to be delivered to each exterior exposure would be determined by a sampling of all of the temperature sensing devices from each of the rooms of the exterior exposure. A value would be arrived at by calculation in a computer, and the selected temperature of air would be mixed at the exterior exposure dampers of each exterior exposure. The volume of that air would be calculated by the computer, and each heating and cooling zone damper would variably open to admit the calculated volume of the air from the distribution duct system into each room.
It is possible that the heating and cooling needs of one particular room of an exterior exposure would have incompatible needs from the other rooms of that exposure. For instance, one room could need cool air, while the other eight rooms needed hot air. In such a circumstance, the computer would sample all of the temperature sensing sites and determine the needs for all of the sites. When an incompatibility is detected, the computer calculates a split delivery schedule of air to rooms with conflicting needs. For instance, for a period of time, the exterior exposure dampers of one exterior exposure would mix air so that heated air goes to the eight rooms which need heated air. During that time, the zone damper in the room which needed cool air would close or go to a minimum setting, and a minimum or none of the warm air would be delivered to that room. After a period of time, the computer would change the mix of hot and cold air at the exterior exposure dampers for the exterior exposure, and send cool air into the distribution duct system for that exterior exposure. At the same time, the heating and cooling zone dampers for the rooms which needed warm air would close or go to a minimum setting, the zone damper for the rooms needing cold air would open, and the cool air would only go to the room which needed cool air. If several rooms needed cool air, each of their heating and cooling zone dampers would adjust to deliver the right amount of cool air to each one to achieve the proper temperature. After a period of time, the heating and cooling zone dampers in the rooms which require cooling would shut or go to a minimum setting, the exterior exposure damper would change the mix to hot air instead of cool air, and the heating and cooling zone dampers of the rooms requiring heated air would variably open to allow the calculated amount of heated air to enter each of those rooms.
This same technique of mixing temperatures could be made even more flexible by the use of a first conditioned air source and a second conditioned air source which can deliver either hot or cold air. Thus, in some circumstances, both of the first main duct system and the second main duct system would contain hot air, and at other times, possibly during the same day and on the same floor and on the same exterior exposure, both the first main duct system and the second main duct system could contain cold air, and deliver this cold air directly to certain rooms but not others.
This system relies on computing ability and the climate control logic to select an air temperature for an exterior heating zone, and to further select an air temperature and air flow from the distribution duct system to flow into each room of the exterior exposure. The system has the advantage of eliminating some of the disadvantages of dual duct HVAC systems, and systems in which heating and cooling capabilities are delivered to each exterior exposure. In the installation of the HVAC system of the invention, when compared with other building heating systems, there is no hot water piping, no chilled water piping, no fan powered terminal VAV boxes, no compressors, and no water valves, pumps or filters in the conditioned space. This system also has the advantage of providing temporary heat availability early in the construction process. This is due to the simple systems inside the occupied space. The system can provide heating, cooling and ventilation air efficiently to any room, zone or small group of similar zones.
Typical installation of the invention would utilize roof mounted heating and cooling systems, but these could also be installed in equipment rooms. A large roof mounted system could supply the heating and cooling needs of many floors and all of the interior and exterior exposures of each floor. If the system were arranged to have a first conditioned air source and a second conditioned air source on each floor, it would work in the same way, with air temperature being selected by voting of the heating and cooling zones, and delivery of air being selected by the heating and cooling zone damper of each individual heating and cooling zone.
A typical building floor plan would have a large interior area in addition to the four perimeter exterior exposures. The cool air for the interior area would typically be fed from the cool air producing conditioned air source. Heating of the interior area would typically not be required, because the interior area would be completely surrounded by heated exterior exposures, which were losing heat to the outside of the building. In certain situations, a particular building or floor may be found to need heated air delivery in the interior area. In that case, heating and cooling zone dampers would be provided for both hot and cold air in the interior zone. The heated and cooled air would come off of the first main duct system and the second main duct system which would typically contain cold and hot air, respectively.
In one configuration of the invention, when it is hot outside, either one or both the first and second conditioned air source become peak cooling units, and cold air is directed into the first and second main duct system. A further optional feature of the HVAC system of the invention is the option of using cold air, below 55xc2x0 F., in one or both of the first and or second conditioned air sources. Utilizing air of this temperature allows ducts to be smaller than would otherwise be possible.
Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description wherein I have shown and described only the preferred embodiment of the invention, simply by way of illustration of the best mode contemplated by carrying out my invention. As will be realized, the invention is capable of modification in various obvious respects all without departing from the invention. Accordingly, the drawings and description of the preferred embodiment are to be regarded as illustrative in nature, and not as restrictive.